1. Field of the Invention
The invention relates to a flow sensor for flowing media, with a cylindrical housing and a sensor element located in the housing, the housing preferably having an outside thread and being screwable into the wall of a pipe or pipe union or into an opening of a connecting piece.
2. Description of Related Art
It was stated initially that the invention relates to a flow sensor. This flow sensor can also be called a flow indicator or flow meter. In addition, the concept of flow-rate sensor or flow-rate indicator is used for these flow sensors. Within the framework of the invention, a flow sensor is defined as both a flow indicator and flow-rate indicator, with which simply the presence or absence of a certain flow is established, and also a flow meter or flow-rate meter in which a flow value is measured, for which therefore a measured value corresponding to the flow value can be obtained.
Known flow indicators or flow meters often operate according to the calorimetric principle. For this purpose, flow sensors generally have at least one temperature measurement element and a heating element. Generally, differential temperature measurement is used. A first temperature measurement element measures the actual measurement temperature, the measurement temperature deriving from the heat output of the heating element, the temperature of the flowing medium and the flow-dependent heat transport capacity of the flowing medium. Furthermore, generally, a second temperature measurement element measures a reference temperature, but the function of the second temperature measurement element can also be assumed by the heating element. In a flow sensor using the calorimetric principle, the temperature measurement element and the heating element constitute the above mentioned sensor element or elements. These flow sensors are relatively expensive, especially compared to conventional proximity switches.
Sensors used to monitor a medium or a property of a medium, such as, for example, the pressure of a liquid or a gas, especially flow sensors, generally have a cylindrical housing, the housing being used, on the one hand, as in all sensors, to protect the sensor and the electronics which belong to it, and on the other hand, also for safe and permanent connection to the pipe carrying the medium or to a tank.
Sensors are designed either for connection to separate evaluation electronics, or are combined with the evaluation electronics as a compact unit. In particular, these compact devices generally consist of at least two parts, a bottom part and a top part, the bottom part being connected to the medium-carrying tank or pipe, and therefore, often also being called a process connection. For this purpose, the housing can be screwed either directly into a correspondingly made pipe section—a tee or process connection—or can be connected together with a special connecting piece as a complete module to the line system of a machine or tank through which the medium to be monitored flows.
Flow sensors can be used in a host of applications. For example, flow sensors can be used in process engineering systems and machine tools. In both cases, flow sensors are used to measure or monitor the flow or flow velocity of a certain medium, for example, air, water, oil or cooling lubricant.
The disadvantage in the above described sensors, especially for a flow sensor—regardless of whether the housing is made in one part or two—is that a pipeline must be cut and a tee must be installed to hold the sensor to connect the sensor or the process connection of the sensor in existing systems. This procedure is especially disadvantageous when the use of a flow sensor is to be combined only with relatively low costs. This is the case, for example, in the water supply in single or multifamily dwellings. A central water supply system in a single or multifamily dwelling generally has a hot water circuit with a hot water tank, a cold water supply and a hot and cold water line with several taps (for example, in baths, kitchen and toilets).